1. Field of the Invention
The present invention relates to an image recording apparatus with functions to record an image on a recording material and to discharge the recording material after recording onto a discharge tray.
2. Related Background Art
Conventionally, image recording apparatus of this kind include image recording apparatus having the functions as a printer, a copying machine, a facsimile machine, and the like and image recording apparatus used as an output apparatus of a composite electronic apparatus including a computer (hereinafter abbreviated as PC) and a word processor, a workstation, and the like.
These image recording apparatus are structured to record an image (including a letter and a symbol) on a recording material such as paper and a plastic thin plate according to recording information.
Recently, such recording apparatus have replaced conventional dot matrix printers and laser beam printers (hereinafter abbreviated as LBPs), ink-jet printers (hereinafter abbreviated as IJPs), thermal printers, and the like have been put to practical use.
Today, LBPs which can carry out tone reproduction with high resolution and high quality, and IJPs which can carry out full color reproduction with photographic image quality are put to practical use.
As the performance of the recording apparatus bodies becomes higher and higher, in order to fully draw out the printing performance of the image recording apparatus, high quality recording media such as glossy paper, glossy films, coated paper and even media dedicated for photographic images are put to practical use.
Therefore, the image recording apparatus bodies are required to be able to record on various kinds of recording media, and together with this, the recording speed of IJPs are required to be comparable to that of LBPs.
The faster recording operation makes shorter the time period until the next recording material is discharged. However, with regard to IJPs, though improvement of ink is in progress, it still takes time to dry the ink.
In this case, a problem arises that the image is degraded if the next recording material is laid on top of the present recording material while the present recording material remains undried.
In particular, in an office, it is often the case that one image recording apparatus is shared by multiple hosts in a network environment. Though ASFs and paper feed cassettes are provided with a mechanism with which a large amount of recording paper can be stored, a recording material after recording is rapidly stacked up at the sheet discharge portion, and the above-mentioned problem is liable to occur.
In order to solve the problem, an apparatus is put to practical use in which a sheet discharge assist plate (hereinafter referred to as a flapper) as an auxiliary retaining member is provided on a sheet discharge tray (discharge tray) of the sheet discharge portion, and a mechanism is mounted which prevents a recording material now being recorded from coming in contact with the recording material which was discharged immediately before the recording material now being recorded at least during the recording operation to gain drying time.
Such an apparatus provided with a flapper is described in the following with reference to FIGS. 9 to 11.
FIG. 9 is a schematic perspective view of an image recording apparatus according to conventional art. FIGS. 10 and 11 are explanatory views of its operation.
In FIG. 9, reference numerals 1, 2, 3, 4, and 5 denote an image recording apparatus body, a sheet feeding device, a recording material, a sheet discharge tray as a discharge tray, and a flapper as an auxiliary retaining member, respectively.
In FIG. 10, the recording material 3 is conveyed in the direction indicated by an arrow a in the figure as an image is recorded thereon by a recording portion which is not shown.
In FIG. 11, when the recording operation ends, by driving the flapper 5 in the directions indicated by arrows b and c in the figure by power from a motor for conveyance or the like which is not shown, the recording material 3 which is discharged after the recording operation and is on the flapper 5 is made to drop in the direction indicated by an arrow d to be stacked on the sheet discharge tray 4.
After that, the flapper 5 is returned to the initial position by operating the flapper 5 in the directions opposite to those indicated by the arrows b and c, and the flapper 5 is ready for the next recording operation.
However, the conventional apparatus described in the above has the following problems.
Since the above-described flapper 5 is structured to be movable over the right and left upper ends of the recording material which is discharged and stacked up, the movable range of the flapper is restricted when the amount of stack of the recording material after discharge becomes large.
FIG. 12 illustrates that the discharged recording material reaches a predetermined value of the amount of stack (the maximum amount of stack).
As can be seen from the figure, if too much recording material is stacked up, the flapper 5 comes in contact with the uppermost recording material, and thus, the operation of the flapper 5 is restricted.
Since the flapper 5 comes in contact with the recording material, not only an image recorded on the recording material is damaged and degraded, but also the operation of the flapper 5 is hindered and the driving system of the flapper 5 is adversely affected.
Further, in case the driving system for driving the flapper 5 branches off from the conveyance driving system for conveying the recording material, the conveyance driving system may also be hindered, and thus it may cause improper discharge.
Though the apparatus body provides a predetermined value as the sheet discharge capacity to draw a user""s attention, particularly in a network environment, it is difficult to give a recording command after confirming the state of sheet discharge of the apparatus body.
The present invention is made to solve the problems of the conventional art described in the above, and an object of the present invention is to provide an image recording apparatus with excellent quality which can prevent image degradation and the like due to stacking too much recording material on a discharge tray.
In order to attain the above object, according to an aspect of the present invention, an image recording apparatus comprising recording means for recording an image on a recording material and an auxiliary retaining member for temporarily retaining the recording material after an image is recorded thereon by the recording means and for dropping the recording material onto a discharge tray to stack the recording material is further provided with detecting means for detecting the amount of stack of the recording material on the discharge tray.
Accordingly, whether the amount of stack of the recording material on the discharge tray is a hindrance or not can be known.
The detecting means preferably has a sensor for measuring the distance from a predetermined position to the surface of the uppermost stacked recording material.
The sensor is preferably provided on the auxiliary retaining member.
The detecting means may have a rotating member one end thereof being pivotally supported and the other end thereof being freely in contact with the uppermost stacked recording material, and detecting means for detecting the rotational angle of the rotating member.
According to another aspect of the present invention, an image recording apparatus comprising recording means for recording an image on a recording material and an auxiliary retaining member for temporarily retaining the recording material after an image is recorded thereon by the recording means and for dropping the recording material onto a discharge tray to stack the recording material is further provided with detecting means for detecting whether the amount of stack of the recording material on the discharge tray reaches a predetermined amount or not.
Accordingly, whether the amount of stack of the recording material on the discharge tray reaches a hindering amount or not can be known.
The detecting means preferably has a switch which comes in contact with the surface of the uppermost stacked recording material when the amount of stack of the recording material reaches a predetermined amount.
The result of the detection by the detecting means is preferably transmitted to a control portion of the apparatus body or to an external device.
The result of the detection by the detecting means is preferably indicated on an indicating portion of the apparatus body or on an indicating portion of an external device.
Presuming means is preferably provided for presuming, based on the amount of stack of the recording material detected by the detecting means, the allowable residual amount of stack relative to the maximum amount of stack of the recording material which does not hinder the operation of the auxiliary retaining member.
The presuming means preferably also presumes the allowable residual number of sheets of stack by comparing the thickness of the recording material on which an image is recorded with the allowable residual amount of stack.
The thickness of the recording material is preferably based on information registered in advance according to the kind of the recording material.
The result of the presumption by the presuming means is preferably indicated on an indicating portion of the apparatus body or on an indicating portion of an external device.
The image recording operation is preferably not carried out when it is judged that there is no allowable residual amount of stack as a result of the presumption by the presuming means.
The auxiliary retaining member preferably comprises opening and closing members provided at both ends, respectively, of the discharge tray in the width direction so as to be freely opened and closed, and retains the recording material with the opening and closing members in a closed state and drops the recording material onto the discharge tray by opening the opening and closing members.
A retaining surface where the recording material is retained by the opening and closing members is preferably substantially flush with a discharging surface where the recording material after image recording is discharged.
A driving source for opening and closing the opening and closing members may also serve as a driving source for conveying the recording material.
The time period during which the recording material after image recording is temporarily retained by the auxiliary retaining member is preferably established such that degradation of a recorded image does not occur between a dropped recording material and the uppermost stacked recording material which is already stacked on the discharge tray.